1. Field of the Invention
The present invention relates to an audio and video synchronizing apparatus and method capable of synchronizing an audio signal outputted from a digital video signal processing apparatus to an external device with a video signal outputted to a display device of the apparatus.
2. Description of the Related Art
A representative digital video processing equipment is a digital TV. The digital TV may be used in connection with peripheral devices such as a DVD, a game player, a VCR, an audio receiver and the like. The digital TV is provided with external device connection ports for the connection with a peripheral device. The digital TV receives and processes audio and/or video signals transmitted from a connected external device, or outputs audio and/or video signals processed by the digital TV to the external device.
FIG. 1 illustrates the configuration of a TV body 10 connected to a VCR 13, an external device, through an audio cable 11 and a video cable 12 of right/left channels. In such a connection state, audio and video signals outputted from the TV 10 may be outputted to the VCR 13 through the cables 11 and 12. Accordingly, the VCR 13 may record the audio and video signals of the TV.
The digital TV provides a high-definition image with superior quality sound. One exemplary method to provide a user with the noticeably high definition image and supreme quality sound is providing an image processing equipment equipped with a signal processor and an output unit, both can satisfy image quality and sound quality. The implementation of the high-definition image is affected by a display device but is not a big issue because most digital TVs are employing display devices allowing the implementation thereof. However, processing an audio signal only with the image processing equipment such as a digital TV has many limitations. For this reason, an audio processing system such as an audio receiver is separately used in many cases. For example, a video signal is viewed using a display device employed by a digital TV, and an audio signal is caught through an audio system connected to the digital TV.
When a user uses an audio system by connecting it to a digital TV, audio/video output ports, so called monitor output ports, provided to the digital TV are used in most cases.
FIG. 2 is a configuration view illustrating that an audio device is connected to a digital TV as an external device. In FIG. 2, an audio output port of monitor output ports of a TV body 30 is connected to an audio input port of an audio device 32 using audio cables 31 of right/left channels. An audio output signal of the right/left channels of the audio device 32 is outputted to each speaker 33. Accordingly, the TV 30 outputs an audio signal to the audio device 32 through the audio cables 31, and the audio device 32, an audio processing system, performs audio signal processing including equalizing, sound field processing, sound effect processing and the like, and thus outputs high quality sound to the speaker 33. In such manner, it becomes possible to provide a user with the high-definition image of the digital TV and the supreme quality sound using the audio device connected as an external device.
However, outputs of the audio and video may not coincide with each other because the time difference exists between an audio signal provided to the audio device through the audio output port of the digital TV and a video signal outputted to the display device. This because it takes relatively long time for the digital TV to process the digital video signal as compared to the time it takes to process the audio signal. Specifically, because the digital video signal contains a larger amount of data than the audio signal and is transmitted with its large amount of data compressed, it takes relatively long time for the digital TV to decode the video signal.
For this reason, in a system where an audio signal is outputted to an external audio device using a monitor output port of a digital TV and a video signal is outputted to a display device of the digital TV, the audio and video are not synchronized because of the time difference between the video output and the audio output of the external audio device.
In order to solve the problem that the outputted audio and video signals are not synchronized, a technology of providing an audio delay function in an audio device has been proposed to delay input audio signal processing for a certain period of time so that the audio signal can be synchronized with the video signal outputted to a display device of a digital TV. However, this method is also problematic in that it is difficult to set an exact period of time during which the audio processing is delayed for the synchronization with the video. This is because the difference in time between video signal processing and audio signal processing is varied depending on digital TVs, a period of time for delay is also varied depending on audio devices, and the time difference of the output exists between the digital TVs and the audio devices.